UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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2022-07-01 16:30

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Conference: Bucharest University Faculty of Physics 2019 Meeting


Section: Solid State Physics and Materials Science


Title:
Influence of grains size on dielectric and piezoelectric properties of BNT-BTx ceramics


Authors:
Alexandra MURARU(1), Ciceron BERBECARU(1)


Affiliation:
1) University of Bucharest, Faculty of Physics, Atomistilor 405, Magurele, Ilfov, Romania


E-mail
mralexandra97@yahoo.com, berbecaru2ciceron@yahoo.com


Keywords:
relaxor BNT-BT, grains growth, nanometric structures, dielectric and piezoelectric properties


Abstract:
(1-x)(Bi0.5Na0.5)TiO3-xBaTiO3 or in short (BNT-BTx) is a relaxor material especially investigated in the present because of environmental protection requirements to replace the toxic lead in piezoelectric applications with performance close to the traditional Lead-Zirconat-Titanate (PZT) ceramics. BNT-BTx ceramics with variable BaTiO3 content were synthesized employing the sol-gel method due to its evident advantages. From structural XRD investigations as obtained ceramics at 200 oC were found to be amorphous with a polymeric like structure and no detectable grains growth. Gel calcinations until around 500 oC evidenced a perovskit like structure with 30 nm grains size and some secondary phases. For samples annealed at higher than 700 oC a pure perovskitic phase was obtained with an averaged grains size around 45 nm. Samples sintered at higher than 1000 oC show a significant grains growth until micronic dimensions. We may suppose that under 900 oC, in the low temperature range grains boundary diffusion process is active whereas in the high temperature range (above 1000 oC) grains boundary migration process influenced the grains growth. In our study we have shown that the dielectric and piezoelectric properties of these ceramics are heavily affected by the nanometric structure of ceramics. Modified domains structure at nanometric scale and especially the 90o domains walls, oxygen vacancies, dipole defects, space charge and charges anchored at the domain walls with pining effect could be also some sources of these modified properties. From this perspective, grains size control becomes one of the most important aspects of the synthesis of these structures.


Acknowledgement:
The authors are indebted to the University of Bucharest for the financial support and cooperatio that made it possible this work.